Economic sanctions have not persuaded North Korea to halt its ballistic missile and nuclear weapons programs or its continued weapons exports. For a long time, the main reason the sanctions did not work was because China would not participate or, if they did, would not do so effectively. China is notoriously corrupt in these matters, something the Chinese government has been forced to admit because of growing public anger over how Communist Party government officials have long resisted attempts to curb their main sources of obtaining personal wealth. But now China has been forced, again by a growing anger among the Chinese public, to make a serious effort to curb domestic corruption and enforce sanctions against North Korea. The sanctions effort has been crippled by corruption, meaning that North Korea could still get a lot of key items for nuclear weapons and ballistic missile development if they are willing to pay the extra costs of larger bribes. The Chinese public, even with a heavily censored local Internet, made it clear they were not happy with a North Korea armed with nuclear weapons while still ruled by a homicidal and increasingly hostile to China tyrant.
Western and now Chinese sanctions have hurt North Korea and crippled its armed forces. The United States, South Korea and even the UN have managed to obtain details of how North Korea partially overcomes many sanctions and that provides a short list of additional sanctions that would mainly hurt the North Korea military and government officials. Most of these will only work if China, and to a lesser extent Russia. cooperates.
In theory, getting China and Russia to halt oil exports would be catastrophic for North Korea. That has happened in the past and eventually forces North Korea to reconsider policies that offended either Russia or China.
China will sometimes cut the tonnage of its oil exports to North Korea but rarely halts all oil exports because that would eliminate any remaining leverage it has over them. Even the threat of Chinese sanctions persuaded North Korea to prepare effective substitutes. One example was the conversion of thousands of trucks to run on coal gas. This sort of thing was popular in Japan and Germany during World War II because of oil shortages, but largely disappeared after 1945. In North Korea these coal powered trucks are common for the same reason. But coal gas is half as efficient as petroleum fuels and vehicles powered by coal gas are slower, have less range and require more maintenance. Coal gas is not suitable for most military vehicles or combat operations. The sluggish and smoky coal powered trucks remind North Korean that their struggle to cope with sanctions is not over yet. Even though China now prosecutes and punishes some businesses that take bribes to help North Korea evade sanctions, there remain a few sanctions, like no oil at all, that would be much more difficult to evade and very expensive if North Korea persisted.
For example, there can be bans on North Korean commercial and military aircraft using foreign airports as well as bans on North Korean seagoing transports. Rail and road traffic into North Korea can be monitored because those can only enter via a few Chinese and Russian border crossings. Such restrictions do not halt North Korean exports and imports but do make those more expensive and time consuming.
The U.S. has been successful at hunting down and punishing major banks and financial institutions that help North Korea move cash to fuel the illegal trade, though this would be more effective if China cooperated. The banking sanctions could be more thorough and be extended to hundreds of individuals, most of them North Koreans, who make the illegal banking network work. That proved impossible because North Korea resorted to using diplomatic officials at their foreign embassies to establish and maintain smuggling operations. This often led to North Korean diplomats getting caught and forced to return to North Korea.
One of the more lucrative exports for North Korea is slave labor. Most of what North Korean workers overseas are paid is taken by an unofficial agent of the North Korean government and then the cash is transported back to North Korea. These legal North Korean migrant workers are part of what amounts to a slave labor program that became a major source of as much as $2 billion a year in foreign exchange. The export of North Korean workers grew from 60,000 men and women in 2014 to over 100,000 in 2016 and continued to grow more slowly after that. The number of workers outside the country is nearly triple what it was before since Kim Jong Un took over in 2011. The North Korean government takes a percentage of the wages these men and women earn outside the country, mainly in Russia and China, and holds the workers’ families hostage in case the worker does not return home when ordered. If someone does not come back, their families are sent to prison camps. Some workers sacrifice their families to be free. Many of these men and women will seek jobs where they can make more money and save enough to afford people smugglers who can get people out of North Korea.
North Korea has long used blatantly illegal exports like addictive substances, counterfeit currency, weapons, stolen data, and technology to keep its nuclear, chemical, ballistic missile programs going. These would become more important if all bulk imports and exports were banned and only food and some medicines were allowed in. Even these imports have been abused, with food aid showing up in Chinese markets near the border, along with medical supplies donated to North Korea. So, it was essential to go after the known corrupt North Korean practices when imposing and enforcing additional sanctions.
More effective sanctions were more essential once the North Korean government decided to allow the possibility of another major famine, like the one in the 1990s that killed 5-10 percent of the population, to develop. The North Korean rulers believe having nuclear weapons will enable them to extort sufficient fuel, food, and cash to turn things around. That turned out to be a fantasy and most of the potential North Korean victims are aware of their vulnerability to chaos in North Korea. China does not want a mass rebellion and government collapse in North Korea, especially when there are nuclear weapons and a lot of other dangerous items involved. That meant the Chinese eventually agreed to support more effective sanctions on North Korea.